First fine the total area of the yard 10 yards x 12 yards = 120 yards^2 Now find the area of the patio in yards 1 yard = 3 ft and each side of the patio is 12 ft --> 4 yards so the patio sides are 4 yds 4 yrds x 4 yrds = 16 yards To find the area of the yard only: 120 yards^2 - 16 yards^2 = 104 yards^2 Krista needs to mow 104 yards^2 total. And she can do 15 ft^2 per minute need the same units so convert the yards to feet 104 yards^2 x 3 ft/yard X 3 ft/yard = 936 ft^2 To find the minutes, divide the total by the amount she can do in one minute: 936 ft^2/15 ft^2 = 62.4 62.4 minutes